1. Field of the Invention
This invention relates to a lifting frame comprising a vertical mast, at least one telescoping lifting mast, and a lift carriage that can be moved up and down on the lifting mast. An accessory hydraulic system can be fastened to the lift mast. At least one hydraulic line discharges at the lift carriage, is installed on the lifting frame, and forms a loop that is open on the top.
2. Technical Considerations
The term “hydraulic line” as used herein includes what are technically called “dual lines”, i.e., a system having two parallel hydraulic lines that are connected to each other and which are generally used as the delivery line and the return line for hydraulic fluid for equipment that uses hydraulic power.
DE 43 35 275 A1 describes a lifting frame which is in the form of a triplex lifting frame. The hydraulic lines for a single-line or dual-line accessory hydraulic system are installed on the lifting frame by means of guide rails (i.e., sections that are open on the side). In this case, the hydraulic lines are inserted, starting from a connection to the vehicle, into the upper end of a guide rail that is fastened to the stationary outer mast (vertical mast) and on the lower end form an open loop before they enter a second guide rail from below. The second guide rail is fastened to the telescoping center mast (lifting mast). The guide rails prevent the hydraulic lines from whipping back and forth and from being squashed when the lifting frame is retracted.
The system described above is complex and expensive to manufacture and install. The guide rails also permanently restrict the driver's field of view in the vicinity of the mast columns of the lifting frame.
The known art also describes how hydraulic lines for an accessory hydraulic system can be wound up on a hose reel and unrolled against spring tension. However, a hose reel cannot be installed inside the dimensions of the lifting frame and, therefore, requires space that must be made available at suitable points of the industrial truck. This limits the amount of space available for the installation of other important components. Seals are also necessary on account of the manner in which the hydraulic line is stored (rotary feed-through), and these seals can fail during operation.
Therefore, it is an object of the invention to provide a lifting frame of the general type described above but which, using simple means and occupying a small amount of space, reduces the time, effort, and expense of installing the hydraulic line for the accessory hydraulic system and which also restricts the operator's field of view as little as possible.